Vegetation trimmers are in common use to cut grass in areas that a mower typically does not reach such as along walkways, fences, and houses. Most trimmers comprise of a filament that is wound around a spool. When the spool is spinning at a high rate, the filament cuts vegetation. A common problem associated with this arrangement is that the force that is generated by the filament in the cutting plane is allowed to act on the filament wound around the spool, thus causing the filament to tangle and this does not permit more filament to pay out from the spool. The operator has to stop the trimmer and disassemble the hub and spool assembly to untangle the filament.
Fixed line trimmers have been developed to completely remove the problem of the filament tangling. The main drawback is that the operator has to stop the trimmer motor in order to refresh the filament multiple times as he is operating the trimmer, thus leading to a shortened life span of the trimmer due to constant starting and stopping of the motor and more time is required to trim an area of vegetation. Some fixed line trimmers use thicker filament than what is most commonly used so the filament does not wear down quickly, but the thicker filament cuts through objects such as exposed wires or wear down fences or walkways against which the operator is trimming. A common practice is to use an extended length of filament in order to increase the amount of vegetation that can be cut without having to refresh the filament, but this poses a serious safety hazard.
Some users of vegetation trimmers purchase pre-wound spools because the filament never tangles. However, the cost of the pre-wound spool is significantly greater than the filament itself. Also, more material is used to make the spool each time the filament runs out than replacing the filament itself. Another common practice is to use a special spool winding mechanism. With the spool winding mechanism, the filament is wound perfectly on the spool so that it does not tangle. The extra mechanism is more expensive to use rather than if the user was able to wind the filament himself. The present invention allows more room for error when the user winds the filament around the spool, thus eliminating the need for replacement of the entire spool or the use of a special spool winding mechanism when the filament runs out.
The present invention directly addresses the causes of the filament getting tangled on a bump feed type trimmer. The filament is clamped between the spool and the hub while the trimmer is running at cutting rpm in order to prevent the force from the filament in the cutting plane from acting on the filament wound around the spool. The spool holds a great length of filament and safely stores it inside the hub until it is fed into the cutting plane once the filament in the cutting plane is worn down.